Jika f (x) = 1/2x - 1 dan f○g (x) = x/3x - 2. Tentukan g○f (-1)

f(x) = 1/2x

(f o g)(x) = (f(g(x)))
x / 3x - 2 = 1/2(g(x))
g(x) = x / (3x - 2) ÷ 1/2
g(x) = x + 2(3x - 2) / (3x - 2)
g(x) = (x + 6x - 4) / (3x - 2)
g(x) = (7x - 4) / (3x - 2)

(g o f)(x)
= g(f(x))
= (7(f(x)) - 4) / (3(f(x)) - 2)
= (7(1/2x) - 4) / 3(1/2x) - 2
= (7/2 x - 4) / (3/2x - 2)

(g o f)(-1)
= (7/2(-1) - 4) / (3/2(-1) - 2)
= (-7/2 - 8/2) / (-3/2 - 4/2)
= -15/2 / -7/2
= -15/7
= 15/7